Sleepless 9 yr old with autism/tourette's, anyone tried melatonin?

My 9 yr old son has a difficult time getting to bed. We have a nightly routine of bath, book, all that stuff. He is autistic and tourette's syndrome. I have been talking with his OT about trying Melatonin. I have read a few things online but nothing conclusive. He has gotten to the point were he is asking for something to help him sleep. I just want him to have a good night sleep and not feel horrible in the morning. Please help,